This invention relates to paper roll web splicing, and more particularly to a concept involving splicing together the new web from a fresh supply roll of paper and the web from a nearly exhausted supply roll of paper in a substantially continuous web feeding operation.
The concepts of the invention can be utilized in association with a large variety of devices wherein a web of paper or other like material is supplied. In such devices, the paper supply comprises a pair of paper rolls which alternately feed a web of traveling paper in substantially continuous fashion to the machine input. When one roll is exhausted, the other roll is substituted. To prevent extensive down time, it has been found desirable to quickly splice the web of a fresh paper roll onto the web of a nearly exhausted roll or a completely exhausted roll which has come free from its core.
In some splicing devices, it is desired to manually feed the leading end of a fresh web to the splicer area at the same time that the expiring web is still running through. The splicer nip area may be inaccessible to the operator, which makes manual feeding or threading very difficult.
For example, the leading edge portion of the fresh web normally has adhesive thereon for application by pressure to the expiring web at the splicing nip. For manual threading, it is necessary to apply the adhesive prior to threading. However, during threading the exposed adhesive may tend to contact and undesirably stick to parts of the splicer upstream of the splicing nip, thus hindering the progress of the web's leading edge toward the nip area.
In addition, it is desired that the leading edge of the fresh web be positioned exactly at the proper point in the splicing nip. With manual threading, it may be possible to attempt proper positioning by visual observation. However, "eyeballing" it is not always fully accurate and furthermore the nip may be positioned within the machine where it cannot be readily or safely observed.
Turning now to handling of the expiring web, it is already known to brake the web to a stop just before the trailing web end reaches the splicing device and so that the splice can be made on momentarily stopped webs. Heretofore, the braking devices have usually comprised a pair of transversely extending paper stop bars between which the expiring web is clamped. The frictional force applied by the clamped stationary bars to the web causes a dragging force thereon until the web comes to a complete stop.
For the most efficient and speedy braking, it is desired to apply a constant brake force during the web slowdown and wherein a minimum time has elapsed. Furthermore, it is desired to brake the web in such a way that the effect of varying web widths and longitudinal tensions in the system is negligable. The aforementioned stop bar system of braking does not lend itself to exact control over these factors.
Broadly, it is a task of the present invention to provide a web splicing apparatus which facilitates manual threading of the leading edge of a fresh web to the splicing nip. More specifically, one task is to eliminate interference between the adhesive coated leading edge portion of the fresh web and the parts of the splicer upstream from the nip. Another task is to automatically position the manually threaded fresh web leading edge exactly at the right spot in the splicing nip without the need for visual observation of the nip area.
It is a further task of the invention to provide a controlled constant rate of expiring web deceleration to brake the web to a stop in the shortest possible time and wherein the effect of various web widths and longitudinal tensions during braking is substantially eliminated.
In accordance with one aspect of the invention, an elongated transverse paper preparation head is provided which has multiple sides. One side is exposed to the operator and the other two back sides form, with suitable guide members, a guide path for threading alternate leading edges of fresh web to the splicing nip area. A spring holds the fresh web to an idler roll upstream of the nip. The fresh web end section is laid across the exposed head side to which a vacuum is applied, and a double faced adhesive tape is applied along the edge portion's exposed face. The edge is then cut off via a knife slot.
The fresh web end section is peeled from the exposed vacuumized side of the head and is manually fed along the guide path. Positive air pressure is applied between the said head back side and the web to cause the web and the adhesive portion to be forced away from the head to eliminate interference therebetween. The moving web floats along its path.
In accordance with another aspect of the invention, the splicer nip roll axes are disposed in a common plane which has a bridging portion extending between the spaced splicer nip roll peripheries during fresh web preparation. The nip roll for the fresh web is adapted to be driven and to have vacuum applied to its surface during said preparation. The construction is such that the fresh web path from the holding spring, across the idler roll and the exposed head face to the knife cut-off slot is exactly equal to the fresh web path from the holding spring, around the idler roll and through the guides to bridging portion of the said plane, which constitutes the actual nip. During manual threading toward the nip, a loose loop is formed in the web. When the leading edge of the fresh web approaches the driven nip roll, it is pulled thereonto by the vacuum and up to the said plane, at which time the web can be visually observed as having tightened around the idler roll.
In accordance with a further aspect of the invention, the previously used basically uncontrolled braking stop bars are replaced by the said spring on one side and the adjacent idler roller on the other side. The idler roller has a high friction surface thereon and has a high inertia due to its mass. A high torque constant braking force is applied to the idler roll which causes the traveling expiring web to decelerate at a constant rate in a controlled minimum time interval. The effects of other external factors are substantially eliminated.